Does a lossless result mean the recording is a studio master?

No. It means the codec in the file can reconstruct its stored samples exactly. A WAV or FLAC made from an MP3 still reports lossless. This check does not prove how the audio was captured.

Which formats can the checker identify?

FLAC, WAV PCM and float, AIFF and common uncompressed AIFC, Apple Lossless, MP3, AAC in MP4, and Opus or Vorbis in Ogg. Other files, including WMA, come back as not identified.

Why is there no audio quality score?

Quality depends on the performance, the microphones, the mix, and the bitrate history. A header cannot measure that. The page reports the codec only.

Is a .wav file always lossless?

No. The usual WAV payload is PCM, which is lossless, but the format code can name a compressed codec. The checker reads that code. The file extension is not the verdict.

Does the checker upload the file?

No. The header is read in the browser. Files over 40 MB are not accepted.

Can it tell Apple Lossless from AAC?

It looks inside the MP4 for an alac box or an mp4a box. Apple Lossless is reported as lossless. AAC is reported as lossy. If both markers appear, the result is not identified.

Lossless audio checker — FLAC, WAV, or lossy

See if a file uses a lossless codec such as FLAC or WAV PCM. Headers are read in the browser — free, no signup.

Audio file

Choose a file to read its codec from the header. Nothing is uploaded.

What does this lossless checker look at?

A lossless codec stores the samples so they can be reconstructed exactly. FLAC, WAV PCM, AIFF PCM, and Apple Lossless are examples. MP3, AAC, and Opus throw information away. This checker reads the file header and reports which of those it found. It does not score sound quality, and it cannot tell whether a lossless file was originally made from an MP3.

What the format test reports

A codec verdict from the header: lossless, lossy, or not identified.

Lossless when the codec says so: FLAC, WAV integer or float PCM, uncompressed AIFF and AIFC, and Apple Lossless in an MP4 container are reported as lossless codecs.
Lossy when the codec discards data: MP3, AAC in an MP4 container, and Opus or Vorbis in an Ogg file are reported as lossy. A WAV whose format code is not PCM is not called lossless.
Unknown when the header is not decisive: WMA can be lossless or lossy, and this check cannot tell which from the ASF header alone. Unrecognized files are marked not identified.
No quality score: The page does not invent a number for clarity, loudness, or production quality. The only answer is the codec stored in the file.
Read locally, up to 40 MB: The bytes stay in the browser. Nothing is uploaded. Files larger than 40 MB are refused.

How to check a file

Use the original download when you can. A re-encoded copy only shows the new codec.

1. Choose the audio file: The checker reads the header in this tab. You do not need an account, and the file is not sent anywhere.
2. Read the verdict: Lossless codec means the container identifies FLAC, PCM, or Apple Lossless. Lossy codec means MP3, AAC, Opus, or Vorbis. Not identified means the header did not match a format this page knows.
3. Treat a converted file as its current codec: Saving an MP3 as WAV or FLAC makes the header look lossless. The checker will say so, and the note on the result explains that the original capture is not proven.

Read the result as a codec check

The header describes how the samples are stored now.

WAV is not automatically lossless: Most WAV files are PCM, which is lossless. A WAV can also wrap a compressed format. The checker uses the format code in the fmt chunk, not the .wav name.
A lossless wrapper can hide a lossy source: If someone converted an MP3 to FLAC, the file is a lossless copy of a lossy encode. Spectral proof of a master is outside this tool.
Do not use the verdict as a listening score: A lossless file can still be noisy, clipped, or poorly recorded. A lossy file can still sound fine for casual playback. This page only names the codec.
WMA needs a different tool: Windows Media Audio includes both lossy and lossless variants. The ASF header this page sees is not enough to separate them, so the result stays unknown.

Sources & References

References for FLAC and for what a WAV header actually stores.

FLAC
“FLAC is a lossless encoding of linear pulse-code modulation data. A FLAC file consists of the magic number fLaC, metadata, and encoded audio.”
— Wikipedia — FLAC
The checker treats a file that starts with fLaC as FLAC and reports that codec as lossless. en.wikipedia.org/wiki/FLAC
WAV
“Though a WAV file can contain compressed audio, the most common WAV audio format is uncompressed audio in the linear pulse-code modulation (LPCM) format.”
— Wikipedia — WAV
The checker reads the WAV format code. PCM and float are reported as lossless. A compressed format code is not. en.wikipedia.org/wiki/WAV

Frequently Asked Questions

Have questions? We have answers.

Explore other diagnostic tools that pair well with this page.

View all tools